1. Field of the Invention
The present subject matter relates to hard disk drives, and more specifically, to managing power of hard disk drives.
2. Description of Related Art
Many computer systems utilize hard disk drives for data storage. Typical hard disk drives today utilize one or more disks coaxially arranged and spun utilizing an electric motor. Data may be written and read using a magnetic head for each disk that “flies” very close to each disk. Data is written by using the heads to magnetize small regions of the disks to a particular polarization and read by using the heads to detect the polarization of each region. The heads are typically driven by an actuator, such as a voice coil actuator, to position the heads the desired distance from the axle of the disks, allowing many different concentric rings of data to be created on each disk. The motor, actuator and magnetic heads may be controlled by a disk controller which also may provide a disk interface that may be used by the computer system to access and control the hard disk drive. The entire hard disk drive may be enclosed in a housing with power and disk interface connections exposed to allow interconnection to the rest of the computer system.
Many computer systems, including servers, desktop and portable computers, may operate in a power saving mode in order to reduce power consumption, both to save on operating costs, as well as for the good of the environment. Some aspects of power saving may be controlled from within the operating system using techniques such as those specified in the Advanced Configuration and Power Interface (ACPI) specification. Other aspects may be managed directly by individual devices. Yet other aspects may be managed explicitly by an application.
Hard disk drives may be a major consumer of power in many computer systems, especially for computer systems such as servers that may utilize a large number of hard disk drives. A hard disk drive may provide one or more low power states of operation. Some of the low power states may turn off the motor that spins the disks as one way of saving power as the motor may be a large portion of the power consumed by the hard disk drive.